What is shoulder dystocia?

Shoulder dystocia is a complication of vaginal birth where the baby’s shoulders get stuck behind the mother’s pelvic bones after the head has been delivered. The umbilical cord gets compressed and can no longer deliver oxygen to the baby, but the baby cannot start breathing because its chest is stuck in the birth canal. Shoulder dystocia can be dangerous for both mother and baby and is an emergency that needs to be treated as quickly as possible.

How common is shoulder dystocia?

Large-scale clinical studies have been conducted to estimate the overall frequency of shoulder dystocia[1,2]. The biggest study, which looked at over 2 million deliveries, found that shoulder dystocia affected around 7 in every 1,000 vaginal births[2].

Can shoulder dystocia be predicted?

Most cases of shoulder dystocia cannot be predicted, but there are certain things about the mother, baby and labour that make it more likely.

Table 1 lists the risk factors that have been associated with shoulder dystocia[3,4]:

 

In pregnancies affected by diabetes, the risk of shoulder dystocia is 2-4 times higher even if the baby is a normal weight[5,6]. A recent Norwegian study of over 2 million deliveries detected shoulder dystocia in approximately 40 diabetic women per 1,000 (compared to 7 per 1,000 without diabetes)[2].

Although these factors are associated with shoulder dystocia, more than half of all cases occur in women who have no risk factors at all[7]. We know that shoulder dystocia is more likely when the baby is bigger than average (>4.5kg), but this is still not a good predictor: firstly, because using ultrasound to estimate the baby’s weight in late pregnancy is not very accurate[8]; and secondly, because most babies weighing 4.5kg or more do not have shoulder dystocia[2,9].

Therefore, even when multiple risk factors are present, we do not have a reliable way of predicting whether or not shoulder dystocia will actually occur[10,11]. The Royal College of Obstetricians & Gynaecologists (RCOG) does not recommend using any sort of shoulder dystocia prediction model[3].

How will the midwife or doctor know that the shoulder is stuck?

All midwives and doctors are trained to recognise shoulder dystocia and know that it needs to be treated as an emergency. If you are having a vaginal birth, once your baby’s head has been born, the midwife will use gentle traction (pulling) to try to deliver the baby’s body. If the body cannot be delivered by gentle traction within the following contraction, this means there is a shoulder dystocia. Once the midwife recognises the shoulder dystocia, they will tell you what is happening and then press an emergency alarm, which will bring lots of people (including senior midwives, anaesthetists, obstetricians and neonatologists, who look after newborn babies) into the room very quickly. This can be very frightening for you and your birth partner but everyone involved will try to reassure you and keep the situation as calm as possible.

Shoulder dystocia management – what will happen during the delivery?

Once the obstetricians have confirmed a case of shoulder dystocia, they will use a step-by-step series of practical techniques (often called “obstetric manoeuvres”) to try to deliver the baby as quickly as possible[3]. These include:

1. Asking you to stop pushing and changing position, moving your bottom to the end of the bed.
2. McRoberts’ manoeuvre: bending both knees and pushing your thighs towards your abdomen.
3. Suprapubic pressure: pressing on your abdomen just above the pelvic bone to help release the baby’s shoulder.
4. Vaginal manoeuvres: these involve an obstetrician inserting their fingers into the vagina to try to release the baby’s shoulder from behind the pelvic bone and to then rotate the baby into a better position for delivery. In this scenario, the obstetrician will normally recommend an episiotomy (a cut to widen the vaginal opening) to give them better access to the baby’s shoulders.

 

The McRoberts’ manoeuvre alone leads to successful delivery in 42% of shoulder dystocia cases[12]. However, if the baby’s shoulder is still stuck after these manoeuvres have been tried, you may be asked to move into an all-fours position and the manoeuvres can be reattempted.

If this does not achieve delivery, there are some “last-resort manoeuvres” that are very rarely required and should be used only by an experienced obstetrician when all other methods have failed. These include deliberately breaking the baby’s collarbone to help release the shoulder, and two other techniques called symphysiotomy and the Zavanelli manoeuvre.

Specialist neonatologists will be present in the room to assess and treat your baby as soon as it is successfully delivered. The midwives and obstetricians will remain with you to identify and treat any immediate complications. You will be offered a full “debrief” (a detailed explanation) on what happened after the delivery once both you and your baby have been stabilised, and you’ll also be given another opportunity to discuss things at a later date.

Complications of shoulder dystocia

Table 2 lists the main complications for shoulder dystocia for mother and baby[13,14]:

 

Third- and fourth-degree perineal tears involve a degree of injury to the anal sphincter. Providing these are identified and repaired promptly, the risk of long-term complications is low. However, a small minority of women will develop chronic problems that can include incontinence (loss of control of faeces or wind)[15].

In the context of shoulder dystocia, brachial plexus injury (also known as Erb’s palsy) occurs when the manoeuvres required to deliver the baby damage the nerves that supply the baby’s arm. This can lead to weakness and abnormal positioning of the arm and hand. Brachial plexus injury following shoulder dystocia occurs temporarily in 3-17% of babies and becomes permanent in 0.5-1.6%. It is usually treated with physiotherapy. It is important to note that brachial plexus injury can occur without shoulder dystocia, including in babies born by Caesarean[16].

Hypoxic-ischaemic encephalopathy refers to brain damage resulting from the baby not getting enough oxygen while the shoulders are stuck. This occurs in 0.3% of babies with shoulder dystocia and usually does not cause long-term problems.

Can shoulder dystocia be prevented by opting for an induction or a Caesarean?

If your baby appears bigger than expected on ultrasound, you may be offered an induction of labour at around 39-40 weeks to prevent the baby from getting even larger before delivery. Induction of labour in this scenario results in lower birth weight, fewer cases of shoulder dystocia and fewer arm or collarbone fractures, and it does not increase the risk of needing a Caesarean. However, it does not reduce the risk of brachial plexus injury[17].

The Royal College of Obstetricians and Gynaecologists (RCOG) recommends elective Caesarean as an option for women who have diabetes and an estimated fetal weight of >4.5kg, due to the significantly increased risk of shoulder dystocia in this group[3]. Other situations in which elective Caesarean may be recommended by your doctor or midwife include:

• Previous shoulder dystocia, especially if there was a severe injury to the baby
• Estimated fetal weight >5kg with no maternal diabetes

If you are worried about shoulder dystocia, ask to speak to a member of your obstetric team, who will discuss your concerns with you. All decisions about how your baby is delivered should be made jointly between you and your obstetric team, who will ensure that you understand all the risks and benefits of each option.

Shoulder dystocia and home births

Shoulder dystocia is unpredictable and can occur in women with no obvious risk factors. If you are giving birth at home and there is a suspected shoulder dystocia your midwife will attempt simple manoeuvres and call an ambulance to transfer you urgently to hospital. Even if the baby is born before the ambulance arrives, it is still advisable to go to the hospital so that you and your baby can be assessed for any signs of complications or injury.

If you have known risk factors for shoulder dystocia, your midwife or doctor will probably recommend that you give birth in an obstetric unit, where doctors are available 24 hours a day.

Main Points

• Shoulder dystocia is a dangerous complication where the baby’s shoulders get stuck behind the mothers’ pelvic bones after the head has been delivered. The umbilical cord is unable to deliver oxygen to the baby as it gets compressed, and the baby can’t start breathing because their chest is stuck in the birth canal.
• Shoulder dystocia is seen as an emergency and needs to be treated as quickly as possible.
• A large-scale study found that shoulder dystocia affects around 7 in every 1,000 vaginal births.
• Several risk factors are believed to increase the risk of shoulder dystocia. There are pre-labour factors, such as gaining a lot of weight during pregnancy and having a big baby, and risk factors that occur during labour, such as the use of an oxytocin drip or having an instrumental vaginal delivery. However, there is no reliable way of predicting shoulder dystocia.
• Pregnant women with diabetes are also at a higher risk of shoulder dystocia; their risk is 2-4 times higher than for women without diabetes.
• However, it’s important to note that more than 50% of all shoulder dystocia cases occur in women with no risk factors at all.
• If your midwife recognises shoulder dystocia, they will press the emergency alarm, which will bring many different medical experts into the delivery room. This can be a frightening experience, but everyone involved will help reassure you.
• The obstetricians will use a step-by-step series of “obstetric manoeuvres” to try to deliver the baby as quickly as possible.
• If the baby is still stuck after the obstetrician has tried all of the manoeuvres, then you may be asked to move into the all-fours position so the manoeuvres can be attempted again.
• There are some “last-resort manoeuvres” that can be attempted if all other methods prove unsuccessful. These rarer techniques, which include deliberately breaking the baby’s collarbone, should only be performed by an experienced obstetrician and, as the name suggests, only when all other methods have failed.
• After the delivery, a specialist neonatalogist will be present to assess and treat your baby. You’ll also be offered a full debrief, where doctors will explain to you what happened during delivery, as there is often no time to discuss this before delivery.
• Shoulder dystocia can lead to perineal tears and postpartum haemorrhage (severe bleeding) after birth. Complications for the baby include damage to the brachial plexus nerves, fracture of the arm and collarbone, and brain damage resulting from insufficient oxygen while the shoulders are stuck.
• Elective caesarean or an induction of labour may be recommended to women who are at increased risk of having a birth affected by shoulder dystocia

References

1. Ouzounian JG and Gherman RB. Shoulder dystocia: are historic risk factors reliable predictors? Am J Obstet Gynecol. 192, 1933-1935 (2005)
2. Øverland EA, Vatten LJ and Eskild A. Pregnancy week at delivery and the risk of shoulder dystocia: a population study of 2,014,956 deliveries. 121, 34-41 (2014)
3. Royal College of Obstetricians & Gynaecologists. Shoulder Dystocia. Green-top Guideline No. 42. Royal College of Obstetricians & Gynaecologists (2012)
4. Kim SY et al., Association of maternal body mass index, excessive weight gain and gestational diabetes mellitus with large-for-gestational age births. Obstet Gynecol. 123, 737-744 (2014)
5. Acker DB, Sachs BP and Friedman EA. Risk factors for shoulder dystocia. Obstet Gynecol. 66, 762-768 (1985)
6. Nesbitt TS, Gilbert WM and Herrchen B. Shoulder dystocia and associated risk factors with macrosomic infants born in California. Am J Obstet Gynecol. 179, 476-480 (1998)
7. Geary M, McParland P, Johnson H and Stronge J. Shoulder dystocia – is it predictable? Eur J Obstet Gynecol Reprod Biol. 62, 15-18 (1995)
8. Rouse DJ, Owen J, Goldenberg RL and Cliver SP. The effectiveness and costs of elective cesarean delivery for fetal macrosomia diagnosed by ultrasound. 276, 1480-1486 (1996)
9. Gross TL, Sokol RJ, Williams T and Thompson K. Shoulder dystocia: a fetal-physician risk. Am J Obstet Gynecol. 156, 1408-1418 (1987)
10. Committee on Practice Bulletins – Obstetrics. Practice Bulletin No 178: Shoulder Dystocia. Obstet Gynecol. 129, e123-e133 (2017)
11. Gupta M et al., Antenatal and intrapartum prediction of shoulder dystocia. Eur J Obstet Gynecol Reprod Biol. 151, 134-139 (2010)
12. Gherman RB et al., The McRoberts’ maneuver for the alleviation of shoulder dystocia: how successful is it? Am J Obstet Gynecol. 176, 656 (1997)
13. Gherman RB et al., Shoulder dystocia: the unpreventable obstetric emergency with empiric management guidelines. Am J Obstet Gynecol. 195, 657-672 (2006)
14. Hoffman MK et al., A comparison of obstetric maneuvers for the acute management of shoulder dystocia. Obstet Gynecol. 117, 1272-1278 (2011)
15. MacArthur C et al., Faecal incontinence and mode of first and subsequent delivery: a six-year longitudinal study. BJOG 112:1075 (2005)
16. Gilbert WM, Nesbitt TS and Danielsen B. Associated factors in 1611 cases of brachial plexus injury. Obstet Gynecol. 93, 536-540 (1999)

Additional useful resources

RCOG Shoulder Dystocia Patient Information Leaflet. https://www.rcog.org.uk/globalassets/documents/patients/patient-information-leaflets/pregnancy/pi-shoulder-dystocia.pdf [Accessed 17/7/2018]

UpToDate Patient Education: Shoulder Dystocia (The Basics). https://www.uptodate.com/contents/shoulder-dystocia-the-basics?topicRef=4472&source=see_link [Accessed 17/7/2018]